Auxiliary contact means for a circuit breaker

ABSTRACT

Auxiliary contact means for a circuit breaker are provided and include an auxiliary movable contact and an auxiliary stationary contact comprising a member projecting from the main stationary contact. The auxiliary movable contact comprises part of an auxiliary contact opening means. The auxiliary contact opening means also serves as arc extinguishing means for the main contacts of the circuit breaker and this combination means is supported on the projecting auxiliary stationary contact member. The main contact and the auxiliary contacts are arranged such that the auxiliary contacts open prior to opening of the main contacts so that the auxiliary contact current is transferred to the main contacts and the auxiliary contacts do not interrupt current. The auxiliary contacts also close after the main contacts so that a closing arc is not struck between the auxiliary stationary and movable contacts.

United States Patent Jawelak et al.

[ AUXILIARY CONTACT MEANS FOR A CIRCUIT BREAKER [75] Inventors: Melbourne G. Jawelak; Richard R.

Boni, McMurray, both of Pa.

[73] Assignee: McGraw-Edison Company, Elgin,

Ill.

22 Filed: July 26,1972

21 Appl.No.:275,333

[52] US. Cl. 200/146 R, 200/150 R, 200/150 G [51] Int. Cl. HOlh 33/12 [58] Field of Search 200/148 A, 150 G, 146 R [56] References Cited FOREIGN PATENTS OR APPLICATIONS 106,334 1/1939 Australia 200/148 A Primary ExaminerRobert S. Macon Attorney, Agent. or Firm-Jon Carl Gealow; Roger F. Falkowski June 25, 1974 [5 7] ABSTRACT Auxiliary contact means for a circuit breaker are provided and include an auxiliary movable contact and an auxiliary stationary contact comprising a member projecting from the main stationary contact. The auxiliary movable contact comprises part of an auxiliary contact opening means. The auxiliary contact opening means also serves as arc extinguishing means for the main contacts of the circuit breaker and this combination means is supported on the projecting auxiliary stationary contact member. The main contact and the auxiliary contacts are arranged such that the auxiliary contacts open prior to opening of the main contacts so that the auxiliary contact current is transferred to the main contacts and the auxiliary contacts do not interrupt current. The auxiliary contacts also close after the main contacts so that a closing arc is not struck between the auxiliary stationary and movable contacts.

6 Claims, 5 Drawing Figures PATENTEDJUHZSIBM 3.8191893 SHEEI 2 OF 5 llllill ixi lll PATENTEDJUN 25 1914 3819.8 93 saw u ur 5 flf lm AUXILIARY CONTACT MEANS FOR A CIRCUIT BREAKER BACKGROUND OF THE INVENTION Power circuit breakers are frequently designed with main and auxiliary contacts in parallel which operate to substantially simultaneously interrupt current in a system flowing through the circuit breaker. Because of the parallel electric connection of the contacts and because of the need for as much compactness as possible in the circuit breaker, the main and auxiliary contacts are located close together. This generally results in a circuit breaker having a complex arrangement of main and auxiliary contacts, the opening and closing mechanism used to operate the contacts and other elements of the circuit breaker such as are extinguishing devices and opening mechanisms that are supplemental to the main opening and closing mechanism. Also, the auxiliary contacts in the circuit breaker are generally intended to interrupt current so that a current arc occurs and the need for auxiliary arc extinguishing means further complicates the overall circuit breaker design.

It is accordingly an object of the invention to provide an auxiliary contact means for a circuit breaker of an economical and simple type. It is a further object of the invention to provide an auxiliary contact means having a stationary contact which is an integral part of the stationary main contact. It is another object of the invention to provide auxiliary contact means which is arranged in a simple and economical manner with auxiliary contact opening means and main arc extinguishing means and which comprises elements of both of the latter two means.

SUMMARY OF THE INVENTION The objects of the invention are accomplished by providing an auxiliary contact means having a stationary contact which includes a projecting portion of the main stationary contact and is positioned immediately adjacent the main contact means. An auxiliary movable contact includes a part of an auxiliary contact opening means which also serves as arc extinguishing means for the main contacts. The combination auxiliary contact opening means and are extinguishing means is supported on the auxiliary stationary contact which projects from the main contact. The main contacts and auxiliary contacts are arranged such that the auxiliary contacts open prior to opening of the main contacts so that auxiliary contact current is transferred to the main contacts and the main contacts provide the only interruption of the current arc. Also, the auxiliary contacts close subsequently to the main contacts so that no closing arc is struck as the auxiliary contacts close. Thus, the continuous current carrying capabilities of the circuit breaker is increased over the current carrying capabilities of the main contacts by the additional current carrying capability of the auxiliary contacts. However, wherein the main contacts carry the total current of both the main and auxiliary contacts only for a short interval of time at opening and closing, it is not necessary to design the main contacts to carry the higher continuous or normal current load.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view of a circuit breaker, partially in cross-section, illustrating auxiliary contact means according to the instant invention;

FIG. 2 is a view of the auxiliary contact means according to the instant invention with both the main and auxiliary contacts means being illustrated in a closed condition;

FIG. 3 is a view similar to that of FIG. 2 during an opening or closing operation of the circuit breaker in which the auxiliary contact means of the circuit breaker is open and the main contact means of the circuit breaker is still closed;

FIG. 4 is a view similar to that of FIGS. 2 and 3 in which the auxiliary contact means is open and the main contact means is just opening and an arc is occurring; and

FIG. 5 is a view similar to FIGS. 2 4 in which both the auxiliary contact means and main contact means of the circuit breaker are in a full open position.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, a circuit breaker is shown as having a metal tank 2 filled with a dielectric fluid 4. Insulator means 6 and 8 are mounted on the tank 2 and extend into the dielectric fluid 4. Main circuit breaker opening and closing means 10 having an insulating rod 11 is mounted on the tank 2 and extends into the dielectric fluid 4 within the tank 2. A circuit interrupter 12 includes stationary interrupter means 14 mounted on the lower end of the insulator means 6, stationary interrupter means 16 mounted on the lower end of the insulator means 8, movable main contact structure 18 connected to the insulating rod 11, and auxiliary contact means 31 and 33. The movable main contact structure 18 includes movable contacts 22 and 24 which are movable into and out of engagement with the stationary interrupter means 14 and 16, as will be later described in detail with respect to FIGS. 2 5. It may be noted that the stationary interrupter means I4, movable contact 22 and auxiliary contact means 31 comprise a half pole assembly. The stationary interrupter means 16, movable main contact 24 and auxiliary contact means 33 comprise another half pole assembly. The two half pole assemblies are electrically connected in series and together comprise a full pole assembly. The insulator means 6 and 8 each enclose an electrical conductor (not shown) connected to an electrical system and to one of the half pole assemblies so that the full pole assembly interrupts the current carried by the electrical conductors.

The stationary interrupter means 14 includes an interrupter housing 26, amain stationary contact structure 28 and auxiliary contact opening means 32. Since the elements of the stationary interrupter means 16 and auxiliary contact means 33 are substantially identical with the elements of the stationary interrupter means 14 and auxiliary contact means 31, they will not be further described in detail. Also, the auxiliary contact opening means 32 is described in detail in copending application Ser. No. 275,332, filed July 26, 1972 and assigned to the assignee of this application. Accordingly, the opening means 32 is described herein only to the extent that it cooperates with the subject matter of the instant invention.

Referring to FIGS. 2 5, the interrupter housing 26 is mounted on the main stationary contact structure 28 and includes an interrupter chamber 38 and movable contact entrance opening 40. The interrupter chamber 38 is of a type well known in the art and will not be further described in detail. As shown in FIG. 1, the main stationary contact structure 28 and the interrupter housing 26 are both below the level of the dielectric fluid 4 and both contain dielectric fluid 4. The main stationary contact structure 28 is mounted on an end of the insulator means 6 and is connected to the previously mentioned conductor (not shown) within the insulator means 6. The main stationary contact structure 28 includes an electrically conductive housing 42 and a main contact spring cluster 44. The spring cluster 44 includes a plurality of contact units each comprising a spring finger 62, a spring 64 and a contact button 66. A pressure relief valve 46 is mounted on the electrically conductive housing 42 for releasing excess gas pressure within the housing 42.

The auxiliary contact opening means 32 includes a cylinder 48 of an insulating material and having chambers 56 and 58 each of which may contain dielectric fluid 4. A pipe 30 connects the interior of the conductive housing 42 and the cylinder 48. The pipe 30 is connected to chamber 58 between the piston means 70 and the projecting members 94 which will be discussed later in greater detail. The chamber 56 has openings 52 and 54 for admitting or exhausting oil into the cylinder 48. The auxiliary contact opening means 32 also includes a piston means 70 slidably movable within the cylinder 48 and separating the chambers 56 and 58. The piston means 70 comprises a piston stem of an insulative material projecting out of the cylinder 48 and a plate check valve 74 having a valve opening 76 and a valve disc 78. The plate check valve 74 operates such that when the piston means 70 moves upward, the pressure of fluid 4 in chamber 56 forces the disc 78 downward and permits fluid 4 to flow through opening 76 into chamber 58. On the other hand, when the piston means 70 moves downward, the pressure of fluid 4 in chamber 58 maintains the disc 78 against the opening 76 so that fluid 4 in chamber 58 is forced downwardly by the piston means 70. A spring 60 is positioned within thechamber 56 for biasing the piston means 70 in a downward direction relative to the view of FIGS. 2 to thereby push the piston stem 72 downwardly and out of the cylinder 48. This action causes pumping of dielectric fluid 4 through the fluid connection or pipe 30 connecting the electrically conductive housing 42 of main stationary contact structure 28 and the chamber 58.

The auxiliary contact means 31 includes stationary auxiliary contact means 34 and movable auxiliary contact means including the cross member 90 and a conductive member 92 which also comprises the lower end of the piston stem 72. It should be noted that piston means 70 and stem 72 are movable independently of the cross member 90. The stationary auxiliary contact means 34 includes the ear or projecting member 94 which extends from and also comprises an integral part of the main stationary contact structure 28. The stationary auxiliary contact means 34 further comprises a spring contact cluster 36 for tightly engaging the lower end of piston stem 72 and which includes a plurality of contact units each comprising a contact button 82, a spring 84 and a spring finger 86. As shown in FIGS. 2 5 the piston stem 72 extends out of the cylinder 48 and through an opening 88 in the projecting member 94. As is also shown in the Figures, the auxiliary contact opening means 32 is mounted and supported on the projecting member 94.

Referring to FIG. 2, the main contact structure 28 and main movable contact structure 18 have a closed condition and the stationary auxiliary contact means 34 and movable auxiliary contact means 20 have a simultaneous closed condition. In this condition of the contacts, the main and auxiliary contact means are electrically connected in parallel and the main contact means carries the major portion of the current in the system to which the circuit breaker is connected. For example, in a particular size circuit breaker, the main contacts carry 3,000 amperes and the auxiliary contacts carry 1,000 amperes. In the closed condition of the auxiliary stationary and movable contact means 31 and 33, the current path for the auxiliary contact means 31 is through the projecting member 94, the spring contact cluster 36, the conductive end 92 of piston stem 72, and thence through the movable auxiliary contact cross member 90. In FIG. 5, the main movable contact 22 is shown in a fully open, disengaged position relative to the main stationary contact structure 28 and spring contact cluster 44. The movable auxiliary contact means 20 and the stationary auxiliary contact means 34 are also shown in a fully disengaged, open condition with the conductive end 92 disengaged from the cross member 90 and spaced from the auxiliary spring contact cluster 36. FIGS. 3 and 4 show the main stationary contact structure 28 and movable contact 22, and stationary auxiliary contact means 34 and movable auxiliary contact means 20 during opening and closing movement intermediate their fully closed and fully open positions or conditions respectively shown in FIGS. 2 and 5.

A contact opening operation may be initiated by actuation of the main circuit breaker opening and closing means 10 which is typically of the spring operated type and is well known in the art. Actuation of the means 10 permits the insulating rod 11 and the cross member 90 to move downwardly so that, in turn, the spring is permitted to discharge from the charged condition shown in FIG. 2 toward its discharged condition shown in FIG. 5. This action of the spring 60 moves the conductive end 92 of piston stem 72 downwardly and applies force to the cross member 90 and the movable contact 22 in a downward, opening direction. As the conductive end 92 and the insulative material of the piston stem 72 move downward through the piston shown in FIGS. 3 and 4, arcing between the stationary auxiliary contact means 34 and the conductive end 92 does not occur so that the insulative material of the piston stem 72 is not subjected to such arcing. This is a desirable aspect of the invention since such arcing would eventually destroy the piston stem 72.

Since an are 68 (see FIG. 4) does not occur between the main stationary contact structure 28 and movable contact 22 during an opening operation, the dielectric fluid 4 within electrically conductive housing 42 and interrupter chamber 38 will be decomposed and a gas (indicated by arrows in FIG. 4) will be generated therefrom. In the event that arcing is sufflciently severe, gas pressure will build up and the gas 80 will flow through the pipe 30 into the chamber 58 and against the piston means 70. Depending on the degree of gas pressure generated, the piston means 70 will either be retarded in its downward movement under the biasing force of spring 60, or it will be stopped and possibly moved upwardly against the spring 60. Consequently, the opening force of the spring 60 will be lessened or completely nullified during the time it normally discharges to aid in providing opening force.

It may thus be seen that a simple and economical auxiliary contact structure for a circuit breaker has been provided which integrally includes part of the main stationary contact structure of the circuit breaker. The movable contact structure of the auxiliary contact means has also been combined with the auxiliary contact opening means and main contact are extinguishing means of the circuit breaker in a simple manner to thereby provide further economies.

While only a single specific embodiment of the invention has been shown herein, it will be realized that many modifications thereof are feasible without departing from the spirit and scope of the invention. It is accordingly intended that the scope of the invention is not to be limited to the specific embodiment disclosed.

We claim:

1. ln a power system including a circuit breaker for conducting and interrupting current and an are created by the current, the combination comprising:

a main stationary contact structure;

a main movable contact structure movable between open and closed positions with said main stationary contact structure;

an auxiliary stationary contact structure comprising an electrically conductive member projecting from said main stationary contact structure;

an auxiliary movable contact structure movable between open and closed positions with said auxiliary stationary contact structure to increase the current carrying capability of the circuit breaker;

said main and auxiliary stationary and movable contact structures being arranged such that upon opening and closing movement of the main contact structures and auxiliary contact structures, the opening of the auxiliary movable and auxiliary stationary contact structures occurs prior to the opening of the main movable and stationary contact structures, and the closing of the auxiliary movable and auxiliary stationary contact structures occurs subsequent to the closing of the main movable and stationary contact structures; and

arcing of said current occurs only between the main movable and stationary contact structures during said opening and closing movement of the main and auxiliary contact structures.

2. The combination according to claim ll wherein:

said movable auxiliary contact and stationary auxiliary contact structure have an open condition; and further comprising an auxiliary contact opening pump mounted on said conductive member and biasing the movable auxiliary contact in an opening direction toward the open condition relative to the stationary auxiliary Contact Stl'UCtUl'G.

3. The combination according to claim 2 wherein said auxiliary contact opening pump includes a cylinder, a piston slidable in said cylinder and piston stern affixed to said piston and extending from said cylinder, said piston stem being an electrical insulator having an electrically conductive end, said end comprising a part of the movable auxiliary contact and engaging the stationary auxiliary contact structure when the latter and the movable auxiliary contact are in their closed condition, said electrically insulating material of the piston stern being positioned between the projecting electrically conductive means and said electrically conductive end during movement of the auxiliary movable contact structure to its open position, said electrically insulating material of the piston stem being free of contact with current arcing while in said position between the projecting electrically conductive means and said end.

4. The combination according to claim 3 wherein: said conductive member has an opening therein; and

said piston stem is movable in said opening direction through the opening in said conductive member. 5. The combination according to claim 3 wherein said stationary auxiliary contact structure includes resilient contact means for providing tight engagement between the movable auxiliary contact and the stationary auxiliary contact structure.

6. The combination according to claim 3 wherein: said main stationary contact structure contains a dielectric fluid, an are being generated during interruption of said current and creating gas from said fluid within the main stationary contact structure;

and further comprising a fluid coupling connecting said main stationary contact structure and said cylinder between said piston and said conductive member, said fluid coupling carrying said gas and dielectric fluid into the cylinder whereby movement of the piston and biasing of the movable auxiliary contact is retarded. 

1. In a power system including a circuit breaker for conducting and interrupting current And an arc created by the current, the combination comprising: a main stationary contact structure; a main movable contact structure movable between open and closed positions with said main stationary contact structure; an auxiliary stationary contact structure comprising an electrically conductive member projecting from said main stationary contact structure; an auxiliary movable contact structure movable between open and closed positions with said auxiliary stationary contact structure to increase the current carrying capability of the circuit breaker; said main and auxiliary stationary and movable contact structures being arranged such that upon opening and closing movement of the main contact structures and auxiliary contact structures, the opening of the auxiliary movable and auxiliary stationary contact structures occurs prior to the opening of the main movable and stationary contact structures, and the closing of the auxiliary movable and auxiliary stationary contact structures occurs subsequent to the closing of the main movable and stationary contact structures; and arcing of said current occurs only between the main movable and stationary contact structures during said opening and closing movement of the main and auxiliary contact structures.
 2. The combination according to claim 1 wherein: said movable auxiliary contact and stationary auxiliary contact structure have an open condition; and further comprising an auxiliary contact opening pump mounted on said conductive member and biasing the movable auxiliary contact in an opening direction toward the open condition relative to the stationary auxiliary contact structure.
 3. The combination according to claim 2 wherein said auxiliary contact opening pump includes a cylinder, a piston slidable in said cylinder and piston stem affixed to said piston and extending from said cylinder, said piston stem being an electrical insulator having an electrically conductive end, said end comprising a part of the movable auxiliary contact and engaging the stationary auxiliary contact structure when the latter and the movable auxiliary contact are in their closed condition, said electrically insulating material of the piston stem being positioned between the projecting electrically conductive means and said electrically conductive end during movement of the auxiliary movable contact structure to its open position, said electrically insulating material of the piston stem being free of contact with current arcing while in said position between the projecting electrically conductive means and said end.
 4. The combination according to claim 3 wherein: said conductive member has an opening therein; and said piston stem is movable in said opening direction through the opening in said conductive member.
 5. The combination according to claim 3 wherein said stationary auxiliary contact structure includes resilient contact means for providing tight engagement between the movable auxiliary contact and the stationary auxiliary contact structure.
 6. The combination according to claim 3 wherein: said main stationary contact structure contains a dielectric fluid, an arc being generated during interruption of said current and creating gas from said fluid within the main stationary contact structure; and further comprising a fluid coupling connecting said main stationary contact structure and said cylinder between said piston and said conductive member, said fluid coupling carrying said gas and dielectric fluid into the cylinder whereby movement of the piston and biasing of the movable auxiliary contact is retarded. 